Aminopeptidase N (membrane alanyl aminopeptidase) is a peptidase that functions in general peptide degradation. This enzyme is located in the small-intestinal membrane and functions in the final digestion of peptides generated from hydrolysis of proteins by gastric and pancreatic proteases (Kruse et al., 1988, FEBS Lett. 239:305–308). There is a need in the art to identify related enzymes, which can be regulated to provide therapeutic effects.